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Impairment Test - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Impairment test [line items]    
Estimated future cash flows pretax discount rate 11.40% 11.90%
Monitoring sensoring and radars CGU [member]    
Impairment test [line items]    
Impairment losses   $ 8.7
Legacy 650 [member]    
Impairment test [line items]    
Impairment losses   $ 50.5
Lineage [member]    
Impairment test [line items]    
Impairment losses $ 61.3  
Lineage [member] | Intangible assets [member]    
Impairment test [line items]    
Impairment losses 58.5  
Lineage [member] | Property, plant and equipment [member]    
Impairment test [line items]    
Impairment losses $ 2.8